1. Field of the Invention
The present invention relates to a light source unit utilizing a light emitting element and a projector utilizing the light source unit.
2. Description of the Related Art
Currently, in many cases, an extra-high pressure mercury lamp or metal halide lamp having a high luminance is used as a light source of a data projector, however, since these light emitting elements have a large heat value, there has been caused a problem that a cooling mechanism becomes complex in configuration and is enlarged in size. Because of this, there have been proposed light sources for small projectors utilizing light-emitting diodes and the like in which heat values are relatively small. For example, the Japanese Unexamined Patent Publication No. 2003-262795 proposes a projector which utilizes a light source in which light emitting elements such as light emitting diodes are arranged into an array.
In the light source unit in which light emitting diodes are used as light emitting elements and a large number of light emitting elements are arranged in the aforesaid manner, light emitting elements are mounted on a substrate to form a light source substrate, and the light source substrate so formed is disposed on a bottom surface of a mirror tunnel formed into a quadrangular prism whose internal surfaces are made into reflecting planes, whereby light reflected on the internal surfaces of the mirror tunnel is configured to be projected in an optical axis direction, and the light so projected is shone on to a display element such as a DMD (Digital Micromirror Device) via a group of lenses and a mirror which constitute a light source side optical system.
In addition, pluralities of red light emitting diodes, green light emitting diodes and blue light emitting diodes are arranged on the light source substrate, and a red light beam, green light beam and blue light beam are projected from the light source unit so as to be shone on to the display element.
In the aforesaid light source unit in which the light emitting diodes are arranged on the bottom surface of the mirror tunnel, in the event that a large number of light emitting diodes are attempted to be arranged thereon, the mirror tunnel has to be thicker, which will disrupt the miniaturization of the projector which utilizes the relevant light source unit.
In addition, when the light emitting diodes are illuminated, the light emitting diodes are badly affected by heat generated by the light emitting diodes disposed adjacent thereto, and to eliminate the bad influence from the adjacent light emitting diodes, the light emitting diodes need to be arranged at predetermined intervals, and when light emitting diodes are attempted to be so disposed on a certain fixed area on the bottom surface of the mirror tunnel, the number of light emitting diodes to be disposed is limited.
Then, in the event that the diameter of the mirror tunnel is increased to accommodate more light emitting diodes in order to increase the quantity of light projected from the light source unit, with the quadrangular prism-shaped mirror tunnel, among light beams which are reflected on internal wall surfaces of the mirror tunnel and are then projected out from the mirror tunnel, the quantity of a light beam which intersects the optical axis of the mirror tunnel at a large angle is increased.
Consequently, the light projected from the light source unit is diffused, and unless a countermeasure is taken in which the number of lens elements in the light source side lens group is increased, or the like, the utilization factor of light is reduced, leading to a problem that an increase in the number of light emitting diodes does not contribute directly to constitute a contribution to an increase in illuminance of the display element.
The invention was made in view of these situations, and an aspect thereof is to provide a small light source which can facilitate the arrangement of a large number of light emitting elements and can shine light projected from the light source unit on to the display element with good efficiency.